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Multislice perfusion imaging in human brain using the C-FOCI inversion pulse: comparison with hyperbolic secant
M N Yongbi1, Y Yang, J A Frank
1Laboratory of Diagnostic Radiology Research, National Institutes of Health, Bethesda, MD 20892, USA.
Magnetic Resonance in Medicine
|November 26, 1999
Summary
The C-shaped frequency offset corrected inversion (FOCI) pulse improves perfusion imaging sensitivity by reducing static tissue signal. This novel pulse increases perfusion signal by 26-30% compared to hyperbolic secant pulses in arterial spin labeling studies.
Area of Science:
- Magnetic Resonance Imaging
- Neuroimaging
- Physiology
Background:
- Pulsed arterial spin labeling (ASL) commonly uses hyperbolic secant (HS) pulses for spin inversion in perfusion studies.
- Optimizing ASL requires matching the inversion pulse slice width to the imaging pulse width, which historically causes artifacts from static tissue signal.
- Current methods to mitigate artifacts, such as widening the HS pulse, increase transit time and reduce perfusion sensitivity due to T(1) relaxation.
Purpose of the Study:
- To evaluate the efficacy of the C-shaped frequency offset corrected inversion (FOCI) pulse in overcoming limitations of HS pulses for multislice perfusion imaging.
- To demonstrate improved slice definition and reduced static tissue contamination in ASL using the FOCI pulse.
- To quantify the increase in perfusion signal achieved with the FOCI pulse compared to the HS pulse.
Main Methods:
- Implementation of the FOCI pulse for multislice cerebral perfusion imaging using a flow-sensitive alternating inversion recovery (FAIR) sequence.
- Comparison of image quality and perfusion signal between FOCI-FAIR and HS-FAIR sequences, with and without vascular signal suppression.
- Quantitative analysis of gray matter perfusion-weighted signal (DeltaM/M(o)) in vivo.
Main Results:
- The FOCI pulse demonstrated superior slice definition in vivo compared to the HS pulse.
- FOCI-FAIR sequences significantly reduced residual static tissue signal, allowing for a smaller gap between inversion and imaging slabs.
- Perfusion signal increased by 26-30% with FOCI-FAIR compared to HS-FAIR, with mean gray matter signal of 1.51% (no suppression) and 0.91% (with suppression) versus 1.19% and 0.64% for HS-FAIR.
Conclusions:
- The C-shaped FOCI pulse effectively overcomes the limitations of HS pulses in ASL perfusion imaging.
- FOCI enables sharper slice profiles, reducing artifacts and increasing perfusion sensitivity.
- This advancement leads to a significant increase in measurable perfusion signal, enhancing the diagnostic potential of ASL.